Beemerboy
XS650 Enthusiast
Are carbs from a 78 special the same as on stock 1975 B model? Are the throttle cable setups the same ? Thanks in advance.
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Carb switching
- Thread starter Beemerboy
- Start date
No they are not the same. The internal parts are all different. If you use them you need to use 78 carb tuning specs. They can b e swapped around and work just fine.
The 78 has linked carbs that use just one throttle cable. They use the same carb holders. The only thing you need to do is remove one of the throttle cables from the throttle housing.
On the 78 carb holders I think they had the ports for vacumm petcocks, if so you can cap them off. Once you get the carbs tuned you can hook the two vacumm ports together for a final step in the tuning process.
I have used a 76-77 set of linked BS38 carbs on my 75 by doing it this way. I currently have a set of 82 BS34 carbs on there now. Just had to use the BS34 carb holders.
The linked carbs have one advantage, being mechanically hooked together they stay synced much better than with the two cable set up where cable stretch can change the sync.
Leo
The 78 has linked carbs that use just one throttle cable. They use the same carb holders. The only thing you need to do is remove one of the throttle cables from the throttle housing.
On the 78 carb holders I think they had the ports for vacumm petcocks, if so you can cap them off. Once you get the carbs tuned you can hook the two vacumm ports together for a final step in the tuning process.
I have used a 76-77 set of linked BS38 carbs on my 75 by doing it this way. I currently have a set of 82 BS34 carbs on there now. Just had to use the BS34 carb holders.
The linked carbs have one advantage, being mechanically hooked together they stay synced much better than with the two cable set up where cable stretch can change the sync.
Leo
Beemerboy
XS650 Enthusiast
Xs, thanks. Any thoughts on VM 34s on a stock ,78 motor versus re-built stock carbs on a tracker project? I would be using pods and I live at 3500ft. I would have the stock carbs re-done by old skool. My,75 has badly leaking carbs as well as a leaking base gasket. Rebuild of the 75 carbs will happen when I have the motor re- done. Your knowledge of these machines is awesome. Thanks for sharing it.
